Lipid soluble extracts of a number of Caribbean marine algae demonstrating biological activity have been identified. High variability in the synthesis of these secondary metabolites has been demonstrated. Presently little is known about the synthesis and conditions which control or influence their production. We have isolated into laboratory culture species of ceramialean red algae which have previously been shown to possess antimicrobial activities. Cultured plants have been demonstrated to produce eicosanoid compounds with autacoid properties in mammalian systems. These red algae are a potentially important source of eicosanoids which may be used as research biochemicals to expedite our understanding of the physiological roles they play in mammalian systems. The physiological role played by these compounds in the organisms that produce them are almost entirely unknown. Key objectives are to determine under controlled culture conditions those physical and/or chemical factors which control or influence the production of the active secondary metabolites and by laboratory manipulation determine the physiological role(s) played by eicosanoid compounds in a red algae. Secondary objectives are to determine which secondary metabolites are responsible for the antibiotic activity and to chemically characterize those compounds.